By Patricia Zengerle WASHINGTON (Reuters) - Republican U.S. Representative Ed Royce said on Monday he will not run for a 14th term representing his southern California district, a seat that could be a key to Democratic efforts to win back control of the House of Representatives. Royce is the latest in a wave of some 30 House Republicans who have announced they are retiring, running for another office or resigning. Democrats need to win 24 seats in the November mid-term elections to retake the majority in the House, which Republicans have controlled since 2011.